The base block is not counted among the n and must be the only block in the bottom layer of the building.
Table of n, a(n) for n=1..9.
Cf. A112389, A123762 - A123827, A123829 - A123849.
Sequence in context: A227101 A024143 A057718 * A233258 A262382 A142895
Adjacent sequences: A123797 A123798 A123799 * A123801 A123802 A123803
Søren Eilers, Oct 29 2006